Currently, a non-aqueous electrolyte secondary battery including a lithium ion secondary battery that is utilized for a mobile device such as a mobile phone is available as a commercial product. The non-aqueous electrolyte secondary battery generally has a constitution that a positive electrode having a positive electrode active material and the like coated on a current collector and a negative electrode having a negative electrode active material and the like coated on a current collector are connected to each other via an electrolyte layer in which a non-aqueous electrolyte solution or a non-electrolyte gel is held in a separator. The charge and discharge reactions of a battery occur as the ions such as lithium ions are absorbed into and desorbed from an electrode active material.
In recent years it has been desired to reduce the amount of carbon dioxide in order to cope with the global warming. Hence, a non-aqueous electrolyte secondary battery having a small environmental burden has been utilized not only in a mobile device but also in a power source device of electric vehicles such as a hybrid vehicle (HEV), an electric vehicle (EV), and a fuel cell vehicle.
As the non-aqueous electrolyte secondary battery for application to the electric vehicles, it is required to have a high output and a high capacity. As the positive electrode active material used in the positive electrode of a non-aqueous electrolyte secondary battery for an electric vehicle, a lithium-cobalt-based composite oxide that is a layered composite oxide has already been widely put into practical use since it can provide a high voltage of a 4V-class and has a high energy density. However, cobalt of a raw material thereof is lacking as a natural resource and expensive so as to be anxious in terms of raw material supply when a possibility that the demand for cobalt is going to significantly increase in the future is taken into consideration. In addition, there is also a possibility that the raw material price of cobalt increases. Hence, a composite oxide containing cobalt at a lower content ratio is desired.
Spinel type lithium manganese composite oxide (LiMn2O4) has a spinel structure and functions as a 4V-class positive electrode material in the composition with λ-MnO2. Spinel type lithium manganese composite oxide has a three-dimensional host structure that is different from the layered structure of LiCoO2 and the like, and thus most of the theoretical capacity is usable so as to be expected to exhibit excellent cycle characteristics.
In practice, however, a lithium ion secondary battery using spinel type lithium manganese composite oxide as the positive electrode material cannot avoid the deterioration in capacity that the capacity gradually decreases as charge and discharge are repeated, and there is still a major problem for the practical application thereof.
As a technology for solving such a problem of spinel type lithium manganese composite oxide, a technology to concurrently use spinel type lithium manganese composite oxide and layered lithium-nickel-manganese-(cobalt) composite oxide containing Ni in a predetermined amount as the positive electrode material is disclosed in JP 2011-54334 A. According to JP 2011-54334 A, it is possible to provide a lithium ion secondary battery capable of achieving both a high output and a long lifespan by taking such a constitution.